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A gamma ray burst, the most powerful explosion known in the Universe, may have hit the Earth in the 8th Century.

In 2012 researchers found evidence that our planet had been struck by a blast of radiation during the Middle Ages, but there was debate over what kind of cosmic event could have caused this.

Now a study suggests it was the result of two black holes or neutron stars merging in our galaxy.

This collision would have hurled out vast amounts of energy.

The research is published in the journal Monthly Notices of the Royal Astronomical Society.

Nature’s snapshot

Last year, a team of researchers found that some ancient cedar trees in Japan had an unusual level of a radioactive type of carbon known as carbon-14.Continue reading the main story “Start Quote

Gamma ray bursts are very, very explosive and energetic events”

Professor Ralph Neuhauser University of Jena, Germany

In Antarctica, too, there was a spike in levels of a form of beryllium – beryllium-10 – in the ice.

These isotopes are created when intense radiation hits the atoms in the upper atmosphere, suggesting that a blast of energy had once hit our planet from space.

Using tree rings and ice-core data, researchers were able to pinpoint that this would have occurred between the years AD 774 and AD 775, but the cause of the event was a puzzle.

The possibility of a supernova – an exploding star – was put forward, but then ruled out because the debris from such an event would still be visible in telescopes today.

Another team of US physicists recently published a paper suggesting that an unusually large solar flare from the Sun could have caused the pulse of energy. However some others in the scientific community disagree because they do not think that the energy produced would tally with the levels of carbon-14 and beryllium-10 found.

So now German researchers have offered up another explanation: a massive explosion that took place within the Milky Way.An image showing a solar flare on 6 March 2012 A solar flare has also been put forward as the cause of the radiation

One of the authors of the paper, Professor Ralph Neuhauser, from the Institute of Astrophysics at the University of Jena, said: “We looked in the spectra of short gamma-ray bursts to estimate whether this would be consistent with the production rate of carbon-14 and beryllium-10 that we observed – and [we found] that is fully consistent.”

These enormous emissions of energy occur when black holes, neutron stars or white dwarfs collide – the galactic mergers take just seconds, but they send out a vast wave of radiation.

Prof Neuhauser said: “Gamma-ray bursts are very, very explosive and energetic events, and so we considered from the energy what would be the distance given the energy observed.

“Our conclusion was it was 3,000 to 12,000 light-years away – and this is within our galaxy.”

Although the event sounds dramatic, our medieval ancestors might not have noticed much.

If the gamma-ray burst happened at this distance, the radiation would have been absorbed by our atmosphere, only leaving a trace in the isotopes that eventually found their way into our trees and the ice. The researchers do not think it even emitted any visible light.

Rare events

Observations of deep space suggest that gamma ray-bursts are rare. They are thought to happen at the most every 10,000 years and at the least once in a million years in a galaxy.Continue reading the main story “Start Quote

The gamma ray burst explanation is about 10,000 times less likely to be true”

Professor Adrian Melott University of Kansas

Prof Neuhauser said it was unlikely Planet Earth would see another one soon, but if we did, this time it could make more of an impact.

If a cosmic explosion happened at the same distance as the 8th Century event, it could knock out our satellites. But if it occurred even closer – just a few hundred light-years away – it would destroy our ozone layer, with devastating effects for life on Earth.

However, this, said Prof Neuhauser, was “extremely unlikely”.

Commenting on the research, Professor Adrian Melott from the University of Kansas, US, said that although he thought a short gamma-ray burst was a possible conclusion, his group’s research suggested that a solar flare was more likely based on observations of Sun-like stars in our galaxy.

He said: “A solar proton event and a short gamma-ray burst are both possible explanations, but based on the rates that we know about in the Universe, the gamma-ray burst explanation is about 10,000 times less likely to be true in that time period.”

Dual-focus contact lens prototypes ordered by Pentagon
LJ Rich By LJ Rich Reporter, BBC Click
iOptik contact lens Innovega says the lenses could be released to the public in 2014
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The Pentagon has put in an order for prototype contact lenses that give users a much wider field of vision.

The lenses are designed to be paired with compact heads up display (HUD) units – glasses that allow images to be projected onto their lenses.

Much bulkier HUDs are already deployed by the US Army and Air Force to superimpose data about targets and other status updates over users’ views.

The tech could help troops enhance their awareness on the battlefield.

The iOptik system’s developer, Innovega, told the BBC it had signed a contract earlier this week to deliver a fully-functioning prototype to the Pentagon’s research laboratory, Darpa.

The US Department of Defense had previously funded part of the Washington-based firm’s initial engineering work on the project.

“The new contract gives us an immediate opportunity to start prototyping and demonstrating elements of this new system,” Innovega’s chief executive Steve Willey said.
Multifocal

The lenses work by allowing the wearer to focus on two things at once – both the information projected onto the glasses’ lenses and the more distant view that can be seen through them.

They do this by having two different filters.

The central part of each lens sends light from the HUD towards the middle of the pupil, while the outer part sends light from the surrounding environment to the pupil’s rim.
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iOptik contact lens

By building two filters into each lens, close-up and distant light sources are both in focus

Watch more about how the iOptik system could transform how we see the world around us

The retina receives each image in focus, at the same time.

“Normally, for example, with a camera you focus on something distant or something close – but you focus on a particular spot,” said Mr Willey.

“By wearing our contact lens you automatically have this multi-focus, or dual-focus, and you are doing something that humans don’t usually do.”
Augmented reality

The chief executive said he also hoped to license the technology to be sold to the public.

One suggested application would be to allow users to watch what appear to be big-screen 3D movies on their glasses – with a different image projected to each lens.

Other potential uses include augmented reality eyewear similar to that teased by Google in its recent Project Glass demo, and a device to offer gamers a more immersive experience.

The lenses are still going through clinical trials as part of the US Food and Drug Administration’s approval process, but Mr Willey said he was confident the tech should be available to the public towards the end of 2014.
Concept graphic of HUD glasses Innovega believes the lenses will allow the use of sunglass-style HUDs with built in projectors
Motion sickness

However, one eye expert suggested that a similar technique had proved problematic when used to treat post-surgery cataract patients.

“Two superimposed images tend to be degraded and lower in contrast,” said Prof Gary Rubin from University College London’s Institute of Ophthalmology.

“I question whether a multi-focal contact lens is the right solution.

“If you’re walking around with a heads up display on, the image projected on the lens could mask your peripheral or central vision. And if it’s magnifying the image or changing the way it moves when your eyes move, you could get motion sickness.”